A microwave oven has been used conventionally as a convenient tool with which food and drink can be heated easily. A container made of heat-resistant plastic sheet and having a hermetically sealed lid, is widely used as a container in which food (including fresh food and processed food) is heated and cooked in a microwave oven.
Among such containers with a hermetically sealed lid, there is a rice cooker for a microwave oven as shown in FIG. 13, the purpose of which is to cook rice. Such a container is described in unexamined Japanese Patent Publication No. 052069/1996. The rice cooker l comprises an inner container 2 containing rice and rice cooking water, an outer container 3 holding the inner container 2 with space between them, an outer lid 4 covering both the outer container 3 and the inner container 2, and a microwave blocking layer 5, provided for convection of rice cooking water in the inner container 2. A water-conducting opening 8 is formed on the inner container 2 so that the inner container 2 may be connected to the outer container 3, and some rice cooking water may flow into space A formed between the inner container 2 and the outer container 3 as heat-retaining water.
Since this rice cooker is heated only from the bottom of the inner container 2 due to the microwave blocking layer 5, it is said to achieve effective convection within its contents, and to prevent boiling over or dehydration due to local heating.
Despite the microwave blocking layer 5 formed on the upper part of the rice cooker, microwave energy received from the side can cause excessive local heating, resulting in uneven heating.
During cooking of rice, ingredients contained in the rice dissolve, forming a paste foam that rises inside the rice cooker. The components of the foam are remixed with the rice by convection. The paste foam contains two kinds of ingredients: gelatinized starch (carbohydrate), which gives rice glutinousness and flavor, and rice bran (fat), which gives rice an unpleasant odor and turns its color from white to yellowish white.
This rice bran has been a problem, since it may not be separated at the time of rice cooking, not only when it is cooked in a conventional rice cooker for a microwave oven, but also when it is cooked in a common electric rice cooker, a gas rice cooker, or a pot heated by gas, charcoal, or firewood etc.
In view of the above problems, the invention aims to provide a rice cooking system for a microwave oven, which is capable of separating and removing rice bran which gives rice a peculiar odor and turns the color of rice to yellowish white; which is capable of heating rice evenly as a whole by preventing sudden local heating; and which generally produces a cooked rice having a superior appearance and flavor.